1. Field of the Invention
The present invention relates generally to methods and apparatus for casting or forming various structures, and more specifically to a fixture providing for both elevation and rotation of a mold. The present fixture is adapted particularly for handling relatively large molds, as used in the forming of boat hulls, decks, and other large components formed of glass fiber and/or similar materials.
2. Description of the Related Art
The invention of methods of forming fine strands of glass fiber and other fine synthetic fibrous materials, means of weaving such materials to form sheets of cloth, and various resins for impregnating such materials to form composite structures, has led to a myriad of different products which were previously formed of other materials. For example, traditionally boats have been constructed of wood, and later riveted and/or welded sheet metal for recreational boats and the like. The development of glass fiber structures made rigid by impregnating with resins and curing, has greatly simplified the construction of such structures and reduced the hours of labor previously required.
Nevertheless, the use of glass and/or other fibers for forming large structures requires a significant amount of specialized equipment, in the form of molds for the hull and other large components, resin mixing equipment, large clean areas for laying out and cutting the glass fiber cloth, etc. Probably the most cumbersome piece of equipment is the mold itself for the boat hull, which is the largest single component of such a craft. Such molds are quite heavy, due to the need for rigidity to form a precisely shaped and dimensioned hull. As a result, they are quite difficult to manipulate, with a number of workers and/or fork lifts, cranes, etc. being required to handle such molds.
Yet, frequent handling is a requirement with such molds, as they typically must be positioned or oriented for access by workers for the layups of glass fiber or other synthetic cloth and resin which are used to form the structure. Such molds are generally rotated or tilted to one side to provide for ease of access for layups along that side of the hull, and then rotated back to the opposite side to facilitate layups on that side. Also, it is critical that the mold be kept very clean, in order to provide the smoothness desired for the completed hull and to preclude contamination of the materials used for the structure. Accordingly, such molds are often stored in an inverted position when not in use. The raising and lowering of such molds is also frequently required, for ease of access to the interior by workers and to provide clearance for rotating the mold from one to another working position or for inversion for storage.
Heretofore, such rotating, lifting, and lowering of relatively large molds was often done by means of cranes and/or fork lifts, using heavy straps and a considerable amount of muscle power by several workers. While some devices have been developed to assist in the movement and orientation of such relatively large molds, none, to the knowledge of the present inventor, provides for complete powered rotation of a large mold as well as providing for powered lifting and lowering of the mold. The present invention responds to this need by providing the above functions, thereby greatly reducing the need for additional equipment in the form of cranes, hoists, lifts, etc., and also greatly reducing the manpower which might otherwise be required for the lifting and/or rotation of a large, heavy mold structure and thereby greatly increasing safety for such workers. A discussion of the related art of which the present inventor is aware, and its differences and distinctions from the present invention, is provided below.
U.S. Pat. No. 4,247,279 issued on Jan. 27, 1981 to William E. Masters, titled xe2x80x9cRotational Molding System,xe2x80x9d describes an apparatus providing periodic heating of two separate molds during curing operations. The molds are on a track which passes through the curing oven, and are alternatingly installed in the oven from opposite ends. Masters also provides a remotely powered system for rocking the molds about their lateral axes, and for rotating the molds about their longitudinal axes. However, Masters does not provide any means of elevating his molds, as provided by the present fixture.
U.S. Pat. No. 4,354,819 issued on Oct. 19, 1982 to Jakob Wirz, titled xe2x80x9cMulti-Pivotable Mold Carrier Clamping Apparatus,xe2x80x9d describes a relatively small clamp table for holding a mold. The Wirz mold carrier has no wheels or casters, and is relatively immobile compared to the present fixture with its wheels which provide a degree of mobility. The two clamp faces are flat plates, precluding placement of a large mold structure having an irregular configuration, such as a large boat hull. While the Wirz device provides for lifting and rotation of the mold held therein, the rotation is about a vertical axis, rather than about a horizontal, longitudinal axis of the mold carried therein, as provided by the present fixture.
U.S. Pat. No. 4,360,334 issued on Nov. 23, 1982 to Gunther Kiefer, titled xe2x80x9cThermoforming Machine,xe2x80x9d describes a machine having three separate compartments for containing a plastic sheet therein, heating the sheet to soften the plastic, and introducing pressure into the mold to form the plastic sheet according to the interior shape of the mold. This process is accomplished via three separate molds and stations, with each handling one of the steps in the process. The forming station provides for elevating the mold for clearance for a deep draw mold. However, Kiefer does not rotate a single mold generally through its longitudinal axis, nor does he provide for elevating the mold by means of a single hydraulic or other powered strut or cylinder, as provided by the present positioning fixture invention.
U.S. Pat. No. 4,632,654 issued on Dec. 30, 1986 to Jerome H. Lemelson, titled xe2x80x9cRotational Molding Apparatus,xe2x80x9d describes an apparatus more closely resembling the rotational molding system of the ""279 U.S. patent to Masters, discussed further above, than the present invention. Lemelson provides only a single mold carriage structure through the heating oven, rather than the two carriages of Masters. However, the same points of distinction between the Masters apparatus and the present invention, i. e., the lack of any elevating means, also apply to the apparatus of the Lemelson ""654 U.S. patent in comparison to the present positioning fixture invention.
U.S. Pat. No. 4,767,299 issued on Aug. 30, 1988 to Peter Friesen, titled xe2x80x9cRotational Molding Machine,xe2x80x9d describes an oven for heating thermoplastic materials during the molding process. The oven contains a rotary drive mechanism providing rotation about two mutually perpendicular axes, unlike the single longitudinal axis provided by the present positioning fixture. It is also noted that Friesen does not provide any means of elevating the mold, either within or without the oven, whereas the present fixture allows the mold to be elevated and lowered as desired to facilitate access thereto. Moreover, the Friesen mold is relatively fixed, whereas the present positioning fixture is relatively mobile, with its wheeled frame.
U.S. Pat. No. 5,028,230 issued on Jul. 2, 1991 to Gordon S. Hunter, titled xe2x80x9cMachine For Handling Molds In Injection Molding,xe2x80x9d describes an apparatus having two opposed mold attachment faces at opposite ends thereof. Both are arcuately translatable so the faces are horizontal, for cleaning and other work. One face is horizontally movable relative to the other, to adjust the spacing therebetween. However, the rotating axes of the Hunter machine are not horizontally disposed and concentric with one another, and thus cannot rotate a single, fixed object therebetween, as provided by the present positioning fixture. Moreover, Hunter does not provide any means of elevating or lowering a mold held within his machine, nor does he provide any means of mobility for the machine, which features are a part of the present invention.
U.S. Pat. No. 5,039,297 issued on Aug. 13, 1991 to William E. Masters, titled xe2x80x9cRotational Molding Apparatus,xe2x80x9d describes a molding oven having two different axes of rotation, with the two axes being non-coplanar with one another. The axes provide a pendular or rocking action for the mold, serving to distribute the casting or molding material more evenly. The apparatus of the Masters ""297 U.S. patent differs considerably from the present positioning fixture invention, in that Masters encloses the entire mold and much of its mechanism within an oven, unlike the present invention. Also, Masters fails to provide any mobility for his apparatus (in fact, a pit or depression is provided for some of the structure), and does not provide any means for elevating the mold, unlike the present positioning fixture.
U.S. Pat. No. 5,458,844 issued on Oct. 17, 1995 to Gary D. MacDougall, titled xe2x80x9cMethod Of Rotary Moulding A Shell Structure Having an Integral Support Structure,xe2x80x9d describes various steps in such a method, using two complementary molds for forming inner and outer shells and sealing the two shells together while the plastic is still in a molten state. MacDougall does not provide any means for manipulating or positioning the molds, whereas the present invention describes only generally a single mold component but describes specifically the means and mechanism for rotating and elevating the single mold as desired.
Finally, Soviet Patent Publication No. 389,982 published on Dec. 13, 1973 to G. P. Markov et al., describes (according to the English abstract) a layup machine for automatically orienting and placing strips or panels of structural fabric onto or into a mold. The device carries a roll of fabric at one side thereof, with gripping means mounted on a track for gripping the free end of the fabric and pulling it out to the desired length or span. The entire mechanism may be turned to orient the weave of the fabric as desired, with the fabric being cut and placed in the mold after orientation and cutting. The Russian Patent Publication fails to disclose any means for rotating or moving the mold, as provided by the present invention. It is also noted that no means for elevating the mold is apparent in the Russian Patent Publication, as provided by the present positioning fixture invention.
None of the above inventions and patents, either singly or in combination, is seen to describe the instant invention as claimed.
The present invention comprises a positioning fixture for a rotary mold, adapted particularly for relatively large and heavy molds as used for forming hulls and related structures for larger boats and the like. The present positioning fixture comprises a generally horizontal frame with an upright at each end, supporting a hull or other mold between the two uprights. The mold supports are adjustable for height, by means of a single lift strut installed at one end of the device. A link (strap, band, chain, etc.) extends from the lifting mechanism at one end of the frame to the lifting mechanism at the opposite end, enabling the single lift strut to lift both ends of the mold together. Safety latches are provided to preclude accidental dropping of the mold.
The two mold supports are pivotable, with one of the supports powered by a rotary motor separate from the lifting strut. This mechanism enables the mold to be rotated for access to any side or area as desired, and to be lifted and lowered as desired for ease of access to the interior of the mold as necessary. The frame is mounted on wheels or casters for mobility in the shop or factory. The rotation motor may be of any suitable type, such as a hydraulic motor powered by a suitable hydraulic supply (pump, etc.). A pneumatic power supply may be used to supply hydraulic pressure and volume to the motor and strut, with air being supplied to the pneumatic pump by a conventional shop air supply. Alternative power means (electric, pure pneumatic, etc.) may be provided as desired and/or where suitable, depending upon regulatory and other concerns.
Accordingly, it is a principal object of the invention to provide an improved positioning fixture for a rotary mold, for rotating and/or elevating the mold as desired.
It is another object of the invention to provide an improved positioning fixture which is adapted particularly for positioning a relatively large mold, as used in the forming of hulls and other structures for relatively large boats and the like.
It is a further object of the invention to provide an improved positioning fixture including wheels or casters for mobility in the local shop or factory environment.
An additional object of the invention is to provide an improved positioning fixture which rotating and elevating means are hydraulically powered, with a pneumatically powered pump providing hydraulic pressure.
Still another object of the invention is to provide an improved positioning fixture including safety latch means for precluding accidental falling or dropping of the mold and lifting mechanism when elevated.
It is an object of the invention to provide improved elements and arrangements thereof in an apparatus for the purposes described which is inexpensive, dependable and fully effective in accomplishing its intended purposes.
These and other objects of the present invention will become readily apparent upon further review of the following specification and drawings.